Displaying 4 results from an estimated 4 matches for "heterocedast".
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heterocedastic
2013 Jan 14
3
How to fit a linear model to data by minimizing the mean absolute percent error?
...e been searching examples for this without any luck:
#Assume
x<-1:10 #x ranges from 1 to 10.
y<-x*runif(10)+ 1.5*x #y is a linear function of x with some error. Add uniform error that is scaled to be larger as x values also become larger
#error is proportional to x size, this should cause heterocedasticity.
#I know there are many methods to deal with heterocedasticity, but in my specific case, I want to use percent regression to minimize the mean absolute
#percentual error as opposed to regular regression that deals with the square of the errors.
#Question, how to fit a linear model to minim...
2006 Aug 03
1
Looking for transformation to overcome heterogeneity ofvariances
Peter
You question is difficult to answer without more information about the
distribution of your residuals. Different residual patterns call for
different transformations to stabilize the variance. One very common
form of heterocedasticity is increasing variance with increasing values
of an independent predictor, i.e. the variance of the residuals of y=x
increase as x increases. In this case a log transformation of some, or
all, of the independent variables of the helps. Please also note the
comment by Bert Gunter (included belo...
2006 Aug 03
3
Looking for transformation to overcome heterogeneity of variances
...ocedasticity
in order to be able to use ANOVA. Unfortunately, no transformation
that I have used transforms my data into data with homocedasticity.
The histogram of variances is at
http://phhs80.googlepages.com/hist1.png
Is someone able to suggest to me a transformation to overcome the
problem of heterocedasticity?
Thanks in advance,
Paul
2003 Oct 04
2
mixed effects with nlme
Dear R users:
I have some difficulties analizing data with mixed effects NLME and the
last version of R. More concretely, I have a repeated measures design with
a single group and 2 experimental factors (say A and B) and my interest is
to compare additive and nonadditive models.
suj rv A B
1 s1 4 a1 b1
2 s1 5 a1 b2
3 s1 7 a1 b3
4 s1 1 a2